1. Field of the Invention
The present invention relates to a motor for driving a rotary color filter that is used for projecting and displaying a color picture image and relates to a display unit employing this motor.
2. Description of Related Art
According to a projector in a DLP (Digital Light Processing) system, by rapidly rotating a color wheel having three color filters of R (red), G (green), and B (blue) (hereinafter, abbreviated as “RGB”) pasted onto a circular disk, a light emitted from a light source is transmitted through these color filters so that the color lights R, G, and B are sequentially extracted. These extracted color lights are illuminated to a predetermined digital micro mirror device (hereinafter, abbreviated as “DMD”) in synchronization with rotation of the color wheel. Then, reflection lights from the DMD are introduced to a predetermined screen and a color picture image is formed and displayed there.
As a conventional motor for rotating a color wheel, one that a shaft to which the color wheel is attached is rotatably supported by a sliding bearing referred to as a sleeve bearing has been known (Japanese Unexamined Pat. App. Pub. No. H05-344675). In this case, the sleeve bearing is made by inserting a shaft in an inner periphery of a sleeve which is impregnated with oil in a cylindrical porous material, and the sleeve bearing serves to support the shaft to be rotated while decreasing friction by forming an oil film between the sleeve bearing and the shaft with oil discharged from the inner periphery of the sleeve.
In the meantime, in the projector in the DLP system, a temperature of inside of a case becomes high due to heat generated from a light source. In recent years, in the projector in the DLP system, an output power of the light source tends to be large in order to improve a picture quality of the projector and a caloric value is also increased. For example, a temperature in the case may be 85° C. and more.
Under such a high temperature environment, a conventional motor for driving a rotary color wheel using the sleeve bearing has a defect that the oil of the sleeve bearing easily vaporizes and the oil is decreased for a short period of time. If the oil is decreased lower than a predetermined amount, the sleeve bearing cannot rotatably support the shaft normally. Therefore, in the conventional motor for rotary driving of a color wheel, an abnormal sound is generated from the sleeve bearing or the picture quality of the projector is deteriorated for a short period of time.
In addition, the conventional motor for driving a rotary color wheel may be attached depending on an arrangement of parts in the case of the projector so that a rotational axis of the motor is attached in the horizontal direction. The motor that is attached in this way cannot be used for a long period of time because the oil of the sleeve bearing easily flows out to the outside due to gravity.